Tin analysis using automated photometric titration

Significance of the Topic

The accurate determination of tin in aqueous solutions is essential for environmental monitoring, metallurgical quality control and industrial process regulation. Automated photometric titration offers a rapid, precise and reproducible approach to assess tin content without extensive manual intervention.

Objectives and Study Overview

This application note describes a fully automated EDTA titration method with photometric end-point detection to quantify tin in its divalent and tetravalent forms. Key aims include demonstrating method robustness, precision and suitability for routine analysis in laboratory and industrial settings.

Methodology and Instrumentation Used

The titration is performed under acidic conditions (pH 2.1) to prevent hydroxo complex formation. Xylenol orange serves as indicator and the equivalence point is monitored photometrically at 574 nm using an Optrode sensor. Sample volumes of 5–15 mL are mixed with buffer and indicator before titration with 0.1 mol/L Na2EDTA. Major instrumental components include:

• 907 Titrando titrator
• 815 Robotic USB Sample Processor XL
• 786 Swing head with titration arm and beaker rack
• 800 Dosino units (5, 10, 50 mL) for reagent dosing
• 802 Magnetic stirrer
• Optrode photometric sensor
• Solitrode reference electrode

Main Results and Discussion

Using six replicate titrations, the method yielded a mean tin concentration of 6.015 g/L with a relative standard deviation of 0.15 %. Key performance parameters:

• Volume increment: 0.05 mL
• Pause and mixing: 30 s pause; stirring rate setting 8
• End-point criterion: 15 mV drift; greatest slope recognition
• Stop volume and stop after EP: 10 mL and 2 mL beyond EP

The low variability demonstrates high precision and the photometric detection ensures clear end-point recognition even in colored or turbid samples.

Benefits and Practical Applications

The automated titration protocol minimizes operator bias, reduces analysis time and enables unattended batch processing. It is suitable for:

• Quality control of tin plating baths
• Routine monitoring of tin leachates in environmental samples
• Research laboratories requiring trace metal quantification

Future Trends and Potential Applications

Advancements may include integration of inline sampling for real-time monitoring, expansion to multi-element titrations with selective indicators, and coupling with chemometric algorithms for improved data interpretation. Further development of sensor technology may extend the method to lower detection limits and a wider pH range.

Conclusion

The described automated photometric EDTA titration provides a robust, precise and user-friendly approach for tin quantification in acidic media. Its high reproducibility and minimal sample preparation make it an attractive option for both industrial and research laboratories seeking efficient metal analysis workflows.